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K-On!'s story revolves around four Japanese high school girls who join their school's light music club to try to save it from being abolished. However, they are the only members of the club, and at first Yui Hirasawa, the main character, has no experience playing musical instruments or reading sheet music. Eventually, she learns how to be an excellent guitar player. Since then, Yui, bassist Mio Akiyama, drummer Ritsu Tainaka and keyboardist Tsumugi Kotobuki spend their school days practicing, performing, or just hanging out together. The club is overseen by music teacher Sawako Yamanaka, who eventually becomes their homeroom teacher as well during their final year of high school. In their second year of high school, the club welcomes another guitarist, an underclassman named Azusa Nakano. After Azusa joins, they gain more structure and begin to practice more. The story concludes at the end of the third year for the senior members. They all agree to attend the same university after high school and leave the club to Azusa after graduation. Yui's sister, Ui, and their friend Jun both join the club for Azusa's senior year. For more: En.wikipedia.org